Currents

More detail

What you see. The color scale runs from still water to about 3.4 knots. On the website the crosshair readout gives the speed in knots when your distance unit is nautical miles.

How to use it. Use it to see where the fast water runs and where it meets slack water, and step the time slider forward to see how the flow is expected to change. For direction, turn on the Currents button on the bottom bar. It is what the short description above calls Current Particles: moving arrows or streaks that show which way the water is going. With the Forecast tab chosen in Data Layers, the streaks follow this same forecast current. In Layer Settings you can change the Colormap, the Range and the Opacity.

How it relates to the other current layers. Currents (DUACS) and Currents (GlobCurrent) are worked out from satellite measurements. They show the big flow only and stop at the present, and the tide hardly shows in either. Currents is the forecast. It includes wind and tide, has finer detail, and reaches up to 7 days ahead. Use Currents (DUACS) for the big flow from the slope of the sea surface alone, Currents (GlobCurrent) to see the same flow with the wind's push added, and the forecast Currents layer for the shelf break, the tide and anything close to shore. All of them share one color scale. Currents at Depth is the same forecast below the surface, down to 656 feet. The Velocity Front layers show this same speed around the rims of eddies only, Retention Zones marks where the water is slack, and Surface Convergence shows where the flow squeezes together.

Who makes it. RipIQ makes this layer itself from the forecast surface current of HYCOM (U.S. Navy model). The layer covers the Gulf of America, the East Coast and Baja.

Its limits. It will not match your drift exactly. Each value covers a square about 5 nautical miles across, and it does not include the push of wind and waves on the boat. There are eight frames a day, three hours apart. The newest frame is from a run started between one and four days ago, and the time slider reaches up to 7 days ahead as a forecast.

The numbers

How often it updates	Once a day, as 8 frames three hours apart
How fresh it usually is	The newest frame is from a run started between one and four days ago
How detailed it is	About 5 nautical miles per grid cell
Where it covers	Gulf of America, East Coast and Baja. Outside the regions the map shows the chart alone; the layers stop at the region's edge.
How far back you can look	8 days back
How far forward you can look	Up to 7 days ahead, as a forecast
Goes blank under cloud?	Never
Observed or modeled	Calculated by RipIQ from HYCOM (U.S. Navy model) fields
What you see on screen	Speed only, no direction. On the website the readout is in knots when your distance unit is nautical miles. The color scale tops out at about 3.4 knots. Surface only

Source: computed by RipIQ from HYCOM model surface currents.